Automatic telephone system



Nov. 3, 1953 F. KESSLER AUTOMATIC TELEPHONE SYSTEM Filed Deo. 51, 1949 5 shets-sheef. 1

FRH/VK KEJSLER Nov. 3, 1953 F. KESSLER AUTOMATIC TELEPHONE SYSTEM Filed Dec. 31, 1949 H5 Nn I I I I 5 Sheets-Sheet.

o ooo op o 4000 ooo ooo o IN V EN TOR.

FRF/VA KEJSLE Patented Nov. 3, 1953 UNITED STATES PATENT OFFICE AUTOMATIC TELEPHONE SYSTEM Frank Kessler, Rochester, N. Y., assignor to Stromberg-Carlson Company, a corporation of New York 6 Claims.

My invention relates to automatic telephone systems, and particularly to automatic telephone Systems having automatic switching means I'or dealing with an incoming line on which a call has been initiated, but from which no impulses have been received.

In automatic telephone systems, calls are normally initiated at a subscribers substation by the subscribers act of removing the receiver (or handset) from the switch hook. The subscriber ordinarily proceeds to select the substation he desires by operating his impulse sending means, usually a dial, in a prescribed manner. The impulse sending means transmits impulses to automatic switching means at a central exchange. This switching means performs the mechanical function of connecting the incoming line from the calling substation to an outgoing line leading to the desired substation.

It sometimes occurs that a call is initiated at a substation, but no impulses are received by the automatic switching means. Such a condition is sometimes referred to as a permanent This may happen, for example, if a subscriber accidentally knocks his receiver or handset ofi its hook, without any intention of making a telephone call. In such cases it is desirable to inform the subscriber that his receiver is oli the hook, since under these conditions he cannot receive incoming calls, and a certain amount of apparatus at the central exchange is kept from the use of other subscribers.

Prior to my invention, it was customary for a trouble man to observe the performance of the automatic switching apparatus. When he noticed that a particular piece of apparatus, such as a selector, had been seized but no impulses had been received over the incoming line, he would inform the wire chief of the fact. 'Ihe wire chief then challenged the line in question; that is, he ascertained whether anyone at the substation was still on the incoming line. If so, he requested the person to hang up; if not, he connected a howler to the incoming line. The howler voltage would cause the receiver at the substation to produce a loud noise, and so induce anyone within hearing distance at the substation to hang up the receiver. This procedure was slow and required the presence of two men. Furthermore, the trouble man might be busy with other duties and not notice that an incoming line was tied up.

It is therefore an object of my invention to provide, in an automatic telephone system new and improved for returning to service.

after a predetermined interval of time, automatic switching apparatus which has been seized by an incoming line but which is not engaged in a connection with an outgoing line.

It is also an object of my invention to provide, in an automatic telephone system, means for indicating to an operator at a manual switchboard that automatic switching apparatus has been seized by an incoming line but that no impulses have been received over that incoming line.

It is a further object of my invention to provide, in an automatic telephone system, switching means automatically operative to connect an incoming line, on which a call has been initiated and over which impulses have been received, to an outgoing line, but automatically operative, if a call is initiated on an incoming line but no impulses are received within a predetermined interval of time, to connect the incoming line to a manual switchboard. In general, I accomplish these and other objects of my invention by arranging automatic switching apparatus, such as a selector of a stepby-step telephone system, to cooperate with timing means for measuring a predetermined interval of time. I arrange the automatic switching apparatus to connect an incoming line to an outgoing line responsive to initiation of a call on the incoming line and the receipt of impulses from that incoming line, and I further arrange [the timing means to cause the automatic switching apparatus to connect the incoming line to a manual switchboard if a call is initiated on the incoming line but no impulses are received over that incoming line within a predetermined interval of time.

In the preferred embodiment of my invention explained herein, I accomplish the foregoing and other objects of my invention by arranging a step-by-step selector to step in both primary and secondary coordinate directions responsive to impulses received over an incoming line in a normal call, but to step automatically only in the secondary coordinate direction if no impulses are received over the incoming line within a predetermined interval of time, as measured by a timing means. By this stepping in the secondary coordinate direction, I provide a means for the incoming line to be connected to a manual switchboard. I also arrange for the actuation of a signal device at the switchboard, whereby the operator thereat is informed that an intercepted call is present on that particular incoming line.

When my invention is applied to a step-bystep automatic telephone System, I prefer to employ an impulse-responsive switch of the flat two direction type. Such a switch may be adapted to step its wipers in two coordinate directions oriented at right angles to each other, a primary coordinate direction and a secondary coordinate direction. However, I wish it to be expressly understood that my invention is applicable to impulse-responsive switches f the Strowger, three-dimensional or other types.

Further objects and advantages of my invention will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming apart of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawing, in which Figures 1, 2 and 3, when laid in numerical order from left to right with corresponding lines in alignment, show a preferred embodiment of my invention.

Specifically, Fig. 1 shows a substation A, a line circuit and a line iinder in block form, together with a schematic representation of part of an impulse-responsive selector circuit embodying my invention;

Fig. 2 shows a schematic diagram of the remaining part of the selector circuit shown in Fig. 1; and

Fig. 3 shows a schematic diagram of a line circuit suitable for use at a manual switchboard in conjunction with the selector shown in Figs. l and 2. Fig. 3 also shows, in block form, connectors, a line circuit and a subscribers substation.

In those parts of the drawings showing the specific wiring arrangements of my invention, conventional schematic representations have been made in the interests of ready comprehension. Specifically, contacts are indicated as belonging to a given relay by a vertical dashed line drawn through them and the Winding of that relay.

The facts that the wipers of the switch move together is also indicated by a vertical dashed line labelled XYR The switch is provided with contact springs known as off-normal springs.

Some of these, indicated as Xen herein, are

operated when the wipers move away from their normal or home position in the first, or X coordinate direction; others, indicated as Yom are operated when the wipers move away from their normal position in the second, or Y, co-

Operation on normal call The operation of the preferred embodiment of my invention will first be explained in conjunction with a normal call, that is, one in which initiation is followed within a reasonable time by the dialling of impulses.

Fig. 1 shows that when a subscriber at substation A removes his receiver or handset from the switch hook, a loop circuit is closed over the incoming line for the operation of relay CBI. This circuit extends from upper winding of relay CBI, contact SW-II and armature SW-I5 of switch through relay SW, tip conductor T extending through the line finder and line circuit to substation A, ring conductor back from substation A line through the line circuit and line 4 finder to armature SW-I8, contact SW-I9, lower winding of CBI to Relay CBI closes a circuit for energizing slowto-release delay relay RDI and for priming the lower winding of relay SW, thereby rendering the latter relay quick to operate. This circuit extends from (I) armature SW-1, contact SW-8, armature CBI-2, contact CBI-3, winding of RDI to the priming circuit for relay SW extends over the path outlined to contact CBI-3, from which it passes through resistor RI and lower winding of SW to Relay CBI also prepares a path for the operation of relay PT, this path extending from the cam spring for timing cam TPI through armature PTI, contact PT2, armature CBI-4, contact CBI-5, and the winding of PT to Upon operation, relay RDI grounds the back sleeve lead S at its contact RDI-4 and armature RDI-3. Relay RDI also closes a circuit for energizing the lower winding of relay XD, this path extending from (-1-), armature HA-4, contact PIA-5, armature RDI-8, contact RDI-1, armature PT-4, contact PT-5, Xen springs I and 1, lower winding of XD to Relay RDI also closes a circuit for lighting the monitor lamp MON, this circuit extending from (-1-), contact RDI-I2, armature RDI-I3, contact SW-I3, armature SW-I2, lamp MON to The foregoing sequence of events is normally followed by the receipt of impulses from substation A. These impulses comprise interruptions of the loop circuit caused by an impulse sending means such as a dial, at substation A. At the beginning of the first loop interruption, the above traced energizing circuit for relay CBI is broken. Relay CBI therefore releases and breaks, at its armature CBI-2 and contact CBI-3, the previously traced operating circuit for relay RDI and priming circuit for the lower winding of relay SW. Relay RDI does not fall back, however, because of its slow release characteristics. Relay CBI also opens, at its armature CBI-4 and its contact CBI-5, the previously prepared operating circuit from the TPI lead to relay PT.

Relay CBI also closes an energizing path for the upper winding of relay XD and stepping relay X, this circuit extending from (-I-), armature SW-'I, contact SW-B, armature CBI-2. contact CBI-I, armature RDI-6, contact RDI-5, previously operated contact XD-5 and armature XID-4, upper Winding of XD to the upper winding of relay XD being in parallel with stepping magnet X. Energization of stepping magnet X causes the wipers XY-I, XY-Z, XY-3 and XY-II each to take one step in the first (X) coordinate direction.

As a result of the movement of the wipers away from their normal position, opposite to (but not engaged with) the contacts in the normal or N level in the switch banks, the Xen springs are operated. Xen springs 6 and 'I consequently opon the previously traced energizing circuit for the lower winding of relay XD while Xen springs 8 and 9 break a point in a possible operating circuit for relay YN. Xen springs 4 and 5 prepare an operating circuit for the release magnet Z of the XY switch.

At the end of the first impulse, the loop circuit including the incoming line is re-closed at substation A, thus re-operating relay CBI. This opens, at armature CBI-2 and contact CBI-I, the previously-traced operating circuit for magnet X. Relay XD remains operated at this time because of its Slow-release characteristics.

The alternate release and re-operation of relay X occurs for each impulse transmitted from the impulse-sending means at substation A over the incoming line, because this results in the alternate release and re-operation of relay CBI. After the end of the last impulse transmitted, relay XD releases.

The release of relay XD results in the energize.- tion of the upper winding of HA, the circuit extending from contact RDI-4, armature RDI-3, armature XID-2, contact XD-I, Yon springs i and 3, upper winding of HA, armature HA-2, contact HA-I to Upon operation, relay HA breaks this circuit at its armature 2, but a holding circuit through resistor R2 is present. The lowered current flow through the upper winding of HA and RT in series makes HA quick to release. Relay HA also completes a path for the operation of switch magnet Y, the circuit extending from armature Z-Z, contact Z-3, Xen springs B and I0, contact 'XD-'I and armature XD-, contact HA-S, armature HA-S, winding of magnet Y to At its armature HA-d and contact HA-3, relay HA places (-1-) on the back sleeve S to mark this selector as busy.

Upon energization, magnet Y causes the wipers of the switch to take one step in the Y coordinate direction, thus engaging them with the first set of contacts in the level at which the switch was previously set as the result of stepping in the X coordinate direction. As the result of making the lirst step in the Y direction, You springs 3 and d are disengaged. This opens a point in the previously-traced energizing circuit for the upper winding of relay HA. Relay HA consequently releases and opens the energizing circuit for magnet Y at contact HA8 and armature HA-9. The release of magnet Y is therefore effective to close a new energizing circuit for the upper winding of relay HA. This circuit extends from on the switch front sleeve contact, armature SW2, contact SW-I, contact RDI-2, armature HDi-I, overflow springs I and 2 of the switch, contact Y-I, armature Y-2, upper winding of HA, armature HA-2 and Contact HA-I to As before, relay HA opens its armature HA-2 to establish its holding circuit through resistor R2.

Relay HA now re-closes, at its armature HA-S and contact HA-B, the operating circuit for magnet Y. Magnet Y thus causes the switch wipers to take a second step, and to open, at armature Y-Z and contact Y-I, the new operating circuit for relay HA. Relay HA consequently falls back and opens the circuit for magnet Y at contact HA-S and armature HA-9.

If the second line in the selected level is busy, ground on the sleeve contact will cause the above enumerated sequence of events to repeat and to advance the switch farther in the Y coordinate direction, until an idle line is found.

Whenever an idle line is found, whether it be the rst line in the level or a subsequent line, the fact will be indicated by the absence of ground on the sleeve contact of that particular line. As a result, the circuit of the Y magnet will not be completed, nor will the circuit for relay HA. It will be noted that, when a busy line is found, the busy identifying sleeve ground extends by way of armature SW-E, contact SW-I, contact R13-2, and armature RD I to one side of the operating winding of relay SW thus shunting the relay and preventing its operation since ground also appears on the other side of the winding of relay SW as extending from contact RD-i, armature RD-t, armature XD-2, contact XD-I, and off-normal spring contacts 4 and 5. When an idle line is found and no ground appears at the sleeve contact, the SW relay operates in series with the HA relay which, however, does not operate as the SW relay operating winding is of much higher resistance than the HA relay winding. This circuit may be traced as follows: ground through contact RDM, armature RD-3, armature XD-2, contact XD-I off-normal spring contacts 4 and 5, operating winding of SW, overvnow spring contacts I, 2, Y magnet interrupter contacts I, 2, HA relay winding, armature HA-2, and contact HA-I to battery.

At its armatures SW-IE and SW-I8, relay SW transfers the tip and ring conductors of the incoming line from relay CBI to the tip and ring .brushes of the XY switch. This action releases .relay CBI and causes seizure of the connector connected to the contacts of the XY switch by means of the outgoing line. Upon seizure, the connector causes the front sleeve contact to become (-l-). Relay SW now locks over a circuit extending from (-i-), the sleeve contact of the selected outgoing line in the banks of the switch, brush 3, armature SW-Z, contact SW-S, baci:

sleeve conductor S, armature DHD-2, contact XD-I, Yon springs 4 and 5, upper Winding of relay SW, overflow springs I and 2, contact Y-I, armature Y-2, upper winding of relay HA, armature HA-2, contact HA-I to Although relay HA is in series with relay SW, relay HA is not operated because it has a much lower resistance than relay SW.

The release of relay CBI opens, at contact CB I-S and armature CB l-2, the energizing circuit for the lower winding of relay SW and the winding of relay RDI. Because of its slow release characteristics', relay RDI drops back after a delay, rather than instantaneously. it will be noted that relay SW connects the front to the back sleeve lead at armature SW-2 and Contact SW-S. The circuit is consequently still marked as busy by ground on the back sleeve lead S when relay RDI releases armature RDI-3.

The operation of relay SW causes lamp MON to be flashed at a distinctive rate, such as l2() times per minute, instead of being steadily lighted, as it was previously. The circuit for accomplishing this may be tr-aced from the lead. marked IPM (120 impulses per minute, which may be supplied from an interruptei` circuit, such as is commonly found in telephone exchanges), contact YN-l, armature YN-S, contact SW-II, armature SW-IZ, lamp MON to This 120 IPM Busy ash indicates that the selector circuit is engaged in a normal call.

If the calling or called party hangs up, ground is removed from the iront sleeve of the selector by mechanism within the connector circuit. Since this front sleeve ground is part of the holding circuit for relay SW, relay SW falls back and re-closes the circuit (including the incoming-line loop circuit) for re-operating relay CBI. 'I'he re-operation of relay CBI re-closes the circuit for relay RDI A circuit for lamp MON is now completed from (-1-), contact HDi-I2, armature RDI-I3, contact SVV-I3, armature SVV-I2, lamp MON to and lamp MON is consequently steadily illuminated.

'I'he release of relay SW also prepares a circuit for the energization of the release magnet Z of the switch when the calling party hangs up. When the latter event happens, the loop circuit for energizing relay CBI is broken at substation A. Relay CBI therefore releases and opens the '-''zn'glY-uit fdr iTelaiyFRD Eat #its COIa iCBI. whe'riaiel'ay-iRlDi #falls-hacha short ti'nie l'atef, llit Lzompletes fa circuit for release magnet Z 'which 'extends i'from contact RDI-I I, 'armature RDI-JIU, v'armature SW-i9, contact fSW-Il, 4Ximspr'ings 4 and '5 (having Yon springs vI iAand 2 inp'arallel), Winding of magnet Z t0 E4(L). 'The `release of relay "RDI also opens the operating fci'rcuit -for lamp MON. Magnet Z releasesfthe'wipeiisfof the switch, and they return 'totheir normal 'lo'r home position. The energizingllcircuit fo'r magnet -Z is broken at both Xen spring 4 and Yon spring IWhen the wipers reach 't'hefnormal position.

During its fenergization, magnet Z causes the "energization o'f lower 'winding of relay HA over fafcircuitextendingfrom -I-`) ,armature Z-2, contact Z-`I, -lowe`r winding 'of relay HA to fRelaylHAthen operates to-ilacegrou'nd (through Lits armature :HA-4 and contact HLA-3) on the y backfsleeve 'leadfSp This insuresthat the selector 'will not be seized until the Z 'magnet is nally ireleased.

lffith'e calling partyha'ngsup first, the battery Ifeed relay in the `connector circuit 'will be releasen, causing :the ground to be removed from -therr'ont-sleeve'contact of thesel'ector. This will cause release of the selector in 'the 'manner as r'stdescribed.

Operation when no impulses are received As previously explained, closure of the incoming line loop at substation A causes the operation `of relay ECBI, which in turn 'operates relay Rb'lypreparesiat its contacts 4 'and 5, a path for the operation of 'relay PT from interrupter cam TP-I 'and closes the 'priming circuit for relay SW. Relay RDI grounds the back sleeve at contacts RDILS and RDI-4, and energizes'the lower winding of relay XD. The latter circuitextends from (li-i), armature HA-4 contact HA-E, armature 4RDI-8, contact RDI-"I, armature PT-II, contact `PT`5, Xen springs 6 'and "I, lower Winding of XD to Relay 'RDI 'also causes the steady illumination'o lamp MON over Aa'circuit extending from (+3), contact RDI-I2, 'armature RDI-I3, 'contact SVV-I3, armature SW''I2, lamp MON to If -no impulses 'are received over the incoming line 'from the impulse sending means at 'substation A, interrupter cam TPI eventually engages its 'contact spring 'to send a lpulse of ground to relay PT. 4Thiscircuit maybe traced 'from (-I-), interruptor cam TPI, cam spring for TPI., armature 'P'T-I, contact PT-2, 'armature CBI-Il, contact CBI-5, winding of 'relay PT to The operation of relay PT causes the 'holding ground 'for the lower winding of relay XD to be transferred from (-1-) at armature HA-II to (-1-) 'from the H2 interrupter cam. 'This circuit may be traced 'from interrupter cam H2, cam spring V'for H2, contact PT-Ii, contact PT-5, Xon springs 'I and 6, lower winding of relay XD to (-4). Relay also completes a path for energizing lrelay YN; lthis circuit may be traced from 4(-i), armature Z-2, contact Z-3, Xen springs 9 and 8, contact PT-9, armature PT-II), winding of relay VYN to Relay YN locks to ground over this lpath because its contact YN-4 and armature YN-S arein .paral-lelwith armature PIT-I and contact 'PT-*9. -Relay YN :prepares a path for v{alaaf-xg 13.00 .ground impulses per minute on 'lamp Mon` These Vpulses ymay be obtained over the '300 -PMlead from some lsource such as a suitable'camon the exchangefinteniupter, for

y"e'xampIe. .I

:inasmuch :as ii-iterrupter "cams 'El 'and :H2

"are-keyed Eto 'the frotatlng 'shaftof the: inter-'runter li'n `thepos-ition Y'indicated in fFig. l1, the 'holding cam H2 has made almost a complete rvolution, `that ris, until @the '1re-cess Ii'n 'the cam Yis =`at fa loositionwhere f its c'a'rn "spring i is disengaged. (Iffdll pulses fshoiild'be r'e'ceiv'e'd be'foe thlstirnefrely willbe released because relafyCBI is intr- 'rupted 'fat the ibeginning of "the rt impulse and "opensthe energizingcircitforfelay Yat "ernia- Iam-fi, Yin 'springs 4 eine 3, upper 'windinggbf 'makeitseifiqiiiekituriease. :RelayH-Ain w-iocks iiirvra iiciiit'eianaiifg ifrbin 1mg) :armature =HA--il,ceiitat armature -XD-z, eiitiiet Y@ springs-wena syiippriwinaiiigfriielay resister im te (ai. `*Relay 'also fueses an operating circuit Iron-nie Y "magnet, fth'i's eiry@uit extending rfr'm ai), armature HAY-f4, edn- -tac't HAas, iai-feature XD-2, contact 1ro-1, Ya, springs fanaa,laiiiigztiireyazfeoritadi *ir-weonta'ct nn-afarlmatiifeiHAL contact Xml, 'irmature VXin-ii, 'ciitatqiAl-fs, "armature winding lof magnet Y to u.

.AS fa result of rits Penergizatioii,1tife Y magnet steps fthe wiper-'s bf ftii'e fs teh iene "siep fin 'the secondary y @ordinate-eiieetianpuiiis engaging ith'e wipers 'with ftiie :niet cbritaets in the iioiiiiai nivel '-N. y 'the wipers inve oir 'nr- 'maL the Yen ieisiitadts are repented. v breaks the above-described -iekliii'g fciiciiit for relay im v aiya springs! lana l3, and riay Irans bak.

whenrfelaymelas's, the 'operati-ng circuit for 'inagn'et Yfisbroke at-'eriiature Hit-'9 fld Contact The Yinagnet bonsequntlyd'rops back. 'The Yan fs'prigs actuated by 'the 'si'n'gle 'step 'the Y direction have, l1"ove`vei',y completed f a circuit for energizing the iippe'i' B4winding ,of relay SW 'which extends 'from (ij- 7contact RDI-4, armature nvm, armaturelxniz, cen- 't'act XD-IL Yen-springs '4 sind 5, iup'perwindin; of sW, XY overflow springs I and 12, vfcoitiidt 1st-1, armature 'ir-"z, "iipper of armature Hit-2, :Contact H-Aj-I to '(j-) L'Allth'ou'gh the upper "winding of H A .is "series with E'the i-'p'pr -v'viiiling fof vremy'svi/2 only {SW operates fbecas'e 'the resistance o'f dHA 1is Iitre'rnely low. Relay Y'SW Yconnects 'the front sleeve to the back 'sleeve at its armature VSW--2 fand 'contact SVV-3; removes ground from the 'operating 'circuit foi rfeiay RDI at its armature `-SW-'I completes 'the previously prepared circuibfor applying 300 'ground impulses per :minute to the MON lamp; 'and :at its armatures SW- I5 and SW-I8 and its contacts SW-'M and `:5W-I1, respectively, extends the tip 'and ring conductors of the incoming line through the tip and ring brushes -of the XY switch 'to -r'eley CB2 at the 'manual switchboard fcsee Fig. '3). The circuit for the dashing of lamp MO vmay be traced from the 300 1PM lead coining fi'o'in a suitable source of interrupted ground pulses, such as` the 'exchange interrupte, ycontact YN-.

armature YN-S, contact SW-l I, amature SW-I2, MON to As previously indicated, CB2 is now energized, the circuit extending from upper winding of CB2, tip contact of the line in the N level of the contact banks of the switch, tip wiper l of the XY switch, contact SW-M, armature SVV-i5, tip side of the incoming line through the preceding circuits to the substation A, ring side of the incoming line through the line circuit and line finder, armature SW-IS, contact SW-ll, ring wiper 2 of the XY switch, ring contact of the line in the N level of the switch, lower winding of CB2 to Relay CB2 closes an obvious circuit for the energization of relay RDZ, which in turn grounds the front sleeve of the selector` at its armature RD2-i and contact BDE-2, and also lights the answer lamp ANS on the face of the manual switchboard over a circuit extending from armature RD26, contact HD2-5, contact I-ID-5, armature I-ID-, listen key springs l and 8, lamp ANS to The act of grounding the back .sleeve provides a holding ground for the SW relay when the RDS relay is released.

Upon seeing the answer lamp lighted, the operator at the manual switchboard may operate the listen key to nd out whether anyone at substation A is on the line. Simultaneously with the operation of this key to connect the operators telephone to the talking conductor of the incoming line, the answer lamp circuit is broken at listen key springs 'I and 8, and at listen key contacts i and 2 an obvious circuit is completed for energizing relay HD. Relay I-ID locks over an obvious circuit to the ground provided at contact HD2-2.

If the operator finds out that no one is on the line, she may operate her howler key to connect the howler to the tip and ring conductors of the incoming line. The howler output is usually a voltage which produces a loud rasping sound in the receiver at substation A. Frequently this sound is suicient to attract the attention of someone in the house or other location of substation A, and lead the person to replace the receiver on the hook.

Lest the operator forget that howler voltage is being applied to one of the incoming lines, relay I-iD is arranged to complete a circuit for flashing the answer lamp to indicate the status of the call being intercepted. This circuit may be traced from the 60 IPM lead 4coming from a conventional source of 60 ground impulses per ininute, contact HD-S, armature HD-d, listen key springs l and 8, and answer lamp ANS to ).v

If the receiver is replaced on the hook at substation A in response to the sound produced by the howler voltage, relay CB2 is released by the opening of the loop connected to the incoming line. Relay CB2 thus releases relay HD2, which in turn removes the holding ground for relay ED to stop the ashing of the ANS lamp, and also removes holding ground from the front sleeve. Removal of this ground results in the release of relay SW. The 300 IPM ground pulses are thus removed from the MON lamp, and a circuit is closed for release magnet Z of the switch. The latter path extends from (-1-), Contact RDi-i i, armature RDI-I0, armature SW-9, contact SW-i t, You springs I and 2, win-ding of magnet Z to Magnet Z energizes the lower winding oi relay IIA for the reason previously explained, and also restores the wipers of the switch to their normal position. The circuit for energizing magnet Zy is broken when the wipers reach their home position because its energizing circuit is broken by the parting of You springs l and 2. While enerhgized, magnet Z breaks the holding circuit for relay YN at its contact Z-3 and YN thereupon drops back. Under these conditions the circuit is restored to its resting or unactuated condition, ready for another call. The de-energization of magnet Z also releases relay HA, which in turn removes ground from the back sleeve to release the line iinder and line circuit.

If the application of howler voltage to the incoming line `does not result in correction of the off-hook condition, the operator at the manual switchboard may call a trouble man to ascertain the difculty. The trouble man can easily locate which selector is occupied with an uncompleted call because lamp MON is iiashing at the rate of 300 times per minute. He can therefore iind out whether the dimculty lies in the central exchange, at the subscribers substation, or possibly on the subscribers line.

While I have shown and described a specific embodiment of my invention, I do not desire my invention to be limited to the particular arrangement herein disclosed, since other modifications will readily occur to those skilled in the art. For example, my invention will work equally well with other rates of ground pulses for the lighting of lamps MON and ANS. Furthermore, it is obvious that my invention could easily be applied to other automatic switching means, or to other types of automatic switches. I therefore intend to cover in the appended claims all modifications Iwithin the spirit and scope of my invention.

What I claim is:

1. In a telephone system, a calling party, a called party, an operator, a two-motion switch havinga set of wipers movable in rst and second directions and having a number of numerical Contact levels giving access to said called party after movement of said Wipers in the first and second directions and a normal contact level giving access to said operator upon movement of said Wipers in the second direction without movement in the first direction, numerical pulse transmitting means controlled by said calling party, timing means, means associated with said switch and effective upon seizure of said switch and receipt 0i' numerical pulses from said puise transmitting means to cause said wipers to be moved in the first and second directions and set upon circuits in said numerical levels for establishing connection between said calling party and said Called party, means Operative to cause said Wipers to be moved in the second direction only to cut in 0n said normal level and establish a connection between said calling 4party and said operator, and means associated with said last named means and said timing means for causing said last named means to be operated by said timing mea-ns if no numerical pulses have been received within a predetermined time after seizure of said switch.

2. In a telephone system, a calling party, a two-motion switch having a set of wipers movable in rst and second directions and having a number of numerical contact levels giving access to a first class of lines after movement of said Wipers in the rst and second directions and a normal contact level giving access to a line of a second class upon movement of said wipers in the second direction Without movement in the iirst direction, numerical pulse transmitting means controlled by said calling party, timingA .1; ineens, ineens. eeseeiatdfwitii said. Sri-.tizia an@ eii-etive -iiiieii seizure Quaid. sfwiteii and. teeeint. fifiiemerieei pulses- `f.i'9m; Seid, puise tias ineens te cause seidiwipers te be iiieyesi in tiiefiiSt. aiid'seeoni, dir eetioiie andSet. unen tir.: 5: etiitsiii Seietfiiuiiiericai. levels ier. establieiiies. eeiiiiettieii between saideailins party anda 0i: Saki-first., eiaSS. 0i. lines,` means operative.. te, Said. Wipers. t9 igeA meiiedin the, eeeondtdi; reetiqironly and; eilt. Saidnermaiieyelieif 19, establishing a ccnneetien-iietween said Galline. party anda line 0f;. Sai .i; second ciass. andmeans eieSeeiettedwitii Said lastnamedmeans andsaid timing. means fereausing said iastnamedmeans, te; Lbereiieriiteel;lei' sa timing. means iin@v nue 15 metieeilnulsesfiiavenheen receivedwithin. a pre.- determined #timev aftergseizure o f said, switch.

TJtif-"In:atelephone:systeiin a calling. party. a calledrparty', anv operator.' a :two-motion switch haring aset; ii-wipersrmovablein first.andtsec-r 2q..

omit-directions andhaving a 'number` ofnumerical..v contact levels giving access to saidmalledmarty; after movement; of,` said; wipers the firstl and second1 directions andianormal contactleyel gv.- ing-- 4access tosaid: operator; upon' movement.VV 0h25: sa-idwipers vin-the secondi direction without/move.- ment inv the first jdirection, numericalpulse trans..-V mittinggmeans 'controlled by said calling party, timing means,l saidztimin'g'means'ineluding ,a irst` tim-,ing-ccircuitfadapted, to be "closed, afterv seizure 3Q. ofsaid,switeh,i saidftiming means also including. a second; timing circuit iestablished: -by` closure. of, said, first-'timingI circuit and adapted. to' be4 openeda predeterminedtime after closure of said.` :first timing circuit;meansl associatedzwth said 35rv switch and eiective upon seizureofjsaidi switch and receiptofinum'erical:pulses-fom said pulse transmitting meansiprioreto -tlieopenilig of saidsecondigtiming vcircuit to'ecause s'aidwipers to be' moved; the `iirst and secondiV directions and. setn 4Q uppn circuits in'-said,'numeificallevelsor establishing connection between sai-d calling party andsaidA ealledpartm means operative to' 'causesaid'r' wipers-tone movediinthe second direction only`y and-.cut in on -saidnormallevel for establishingy 45 a cpnnectiongbetweenfsaid :calling partyandsaid operator,` and., Ameans*` associated: lwith said' last named 'means landjif said ,timing means for cau's-v ing-said Iastmamedmeans to be operated iin re-" sponseto, the.; opening -of `saidsecond timing" cir.- 50. cuit-i;f no numerical pulseshave been' receivedr priorto .the opening' of-,said .second .timing circuit. 4,;Inj-aytelephonef systemya calling party, a* twgymotion switlr having a setof-wi'pers movablejnfirsty-andsecond' directions andliaving a '554 numberofmumericalgcontact levels giving-access to' 9.(rnstlclaissgof lines after vmovement of s'aid'' wipersuirky tlie rst pand; second directions and a normalonytactlevelgiving. access to a line of la'` second'classuppn movement'of said Wipers inoA th second Vdirection -without:movement. in the rt dire n, numerical pulse transmitting means controlled,;byg said; calling party,1 timing*- means, said timing means including a first time"Vv ingfcirculit adaptedsto'gbe.closedafter seizure of 65 saidswi saiggtiniingmeans alsoinclu'ding aY second timing circuit eestajolished byelosure of said stt in?,T c'ircit anidladaptedito, beiopenedia after closure of-sad .;rst

ne.` Qi Saideegoiid class, anti-.ineens with. Saitiiiast ne, ed -.me aris.eiiii.Said ti... nameansict eeiiiSiiiig.Saifitiastnamed.ineensz t9. e tpeietedtinres rise to .thepenine et said: Se i'iiii sei. 11.1 linie numerit-eiiiulseshatia, beenieeeitedsnritrtq.the opening,i ofaici secondi; timing circuit.

5r Iiiateieniinnexstem. aeellinapariy, 11.1.1.-

me piiieetransm' tiiiameans,centralisatie. Sai. fealliiiapatty. at metieii SteppingL having a. banisoia eaiitaets-disposedin eiiiumbei-v 0i ielejiiieiufiiiiaa neitmai. leyel, aset oftwipe. ers, for seietiiveixenaagiiig said contacts. aiiriitV magnet. fait. ineviiiasaid wipers ina. iiirstieyei; 'Seietiiiie di eeiiiin. a.See..0.1i.f.i.` magnet. for. mov. iiile,..Saii.iniiieretiii .Seegiitidireetieninio alena.` Seid.. Snitch. hanne; aeseciaieti therewith. Si.w Change-Oven. reiay.. eieetiite 11190.11 opeiation..

en tiiiitai-teireiiit. eiosesi incident, to.

'0i Seid Sw'teh. te`r neetsaid firstfniasnetintc e eiieiiitteeiitrgiiedibaSaid numeiieeipuiSes and... eiiettive linen release tavdistciirieet; saisi.;first.;-A meeiietfeiiii eeiiiieet, Seid. Secfincif;rifiasiieti int-9i. an... eiitomaiiemiiSi. e.. eireiiit a nist,... helding..

Patty and as 'eiitiiitiei met tai ne oneratetieaidlchangea;

over.. relax. din increment.' ei..-'Seid. in.. 1e l-.Seieetiiia direction, meeesfcn id` iStfhQitiiiiaeireuit; aiiti;.eai,1.e.ina Seisiiieiieeaeiientelai.,tecieiease,.respqneixeltta. the termination of a series of numericaL-pgls'esi ieiiieieiey .eaiiSe Said.; Seeeiitiamesiietite-.eiii mati .iii-'meile i .impersinthesecondf iieii.. inte.. engagement; Witiit. egiiiaetslin levels` Oiiie thee Seititrierineti ieiei. timing,.means e.. SePiPIiiifhQidiii Qiiiiii i9 .,maiiitainiiig.; nerats. ed.. aid' .vei...ie1.ey... meaiiS .'eeiitroiied; by... Seid. iiiiiiiia. feimiiaiiSieriiiiasaisi.;ebene. Wetieiay frein Seid iirStiiQiiiins circuit tQ- se'd SetQiiithQltiiiie.; e..i,.r..e.i.i.ii.i after..A Seizure 0f i Se .i switch, and means controlledz-,bygsaid timingy meetiS te enen, Setisi.-..Set.fiiit1.=.l @time circuit .and

` Seid eiiaiiee-Oveireley. if neynumerieai t heeaieqeiyeii Within..- e lpretieteia.

miiied ima-...ettenSeifheiiaiigezever..reiayeiies..

@wie

an auto lrst level selecting direction, means for opening said first holding circuit and causing said change-over relay to release responsive to the termination of a series of numerical `pulses to thereby cause said second magnet to automatically move said Wipers in the second direction into engagement with contacts in va level other than said normal level, timing means, said timing means including a rst timing circuit adapted to be closed after seizure of said switch, said timing means also including a second timing circuit established by closure of said rst timing circuit and adapted to be opened a predetermined time after closure of said rst timing circuit, a second holding circuit for maintaining operated said change-over relay, means controlled by closure of said rst timing circuit for transferring said change-over relay from said rst holding circuit to said second holding circuit after seizure of said switch, and means controlled by opening of said second timing circuit to open said second holding circuit and restore said change-over relay if no numerical v mined time after said change-over relay has -been transferred to said second holding circuit to thereby cause said second magnet to automatically move said Wipers in the second direction into engagement with said contacts in said normal level Without previously moving said wipers in the rst level selecting direction.

FRANK KESSLER.

References Cited in the le 0f this patent UNITED STATES PATENTS Number Name Date 1,541,386 Polinkowsky June 9, 1925 1,896,757 Strickler Feb. 7, 1933 2,010,365 Hoefert et al Aug. 6, 1935 2,143,971 Brazelton Jan. 17, 1939 2,183,649 Kahn Dec. 19, 1939 2,261,243 Flint NOV. 4, 1941 2,504,708 Long Apr. 18, 1950 2,567,650 Morris Sept. 11, 1951 

